A hybrid electric vehicle (HEV) powertrain includes an engine and an electric motor, wherein torque (or power) produced by the engine and/or by the motor can be transferred through a transmission to the vehicle drive wheels to propel the vehicle. A traction battery supplies energy to the motor for the motor to produce the motor torque for propelling the vehicle.
In certain configurations, the engine is connectable to the motor by a disconnect clutch and the motor is connected to the transmission. The engine, the disconnect clutch, the motor, and the transmission are connected sequentially in series.
The electric motor may start the engine by providing torque to crank the engine. In very cold temperatures (e.g., below 20 degrees Celsius), however, the output of an associated high voltage battery is significantly reduced. Thus, the torque produced by the electric motor alone may not be sufficient to crank the engine.
Some HEV's may be provided with a low voltage (e.g., 12V) starter to assist the electric machine in starting the engine. In some approaches, the low voltage starter includes a belt integrated starter (BIS or BISG) that includes a belt drive connecting a crankshaft of the engine to the BIS(G). In very cold temperatures, the BIS(G) may experience belt slip.